1. Field of the Invention
The present invention relates to an on-vehicle apparatus, a preceding vehicle position determining apparatus, and a preceding vehicle position determining method.
2. Description of the Related Art
In the related art, techniques that identify the positions of objects around a host vehicle have been developed.
For example, Japanese Patent Application Publication No. 2002-222491 (JP-A-2002-222491) describes a technique that recognizes a preceding automobile in the vicinity of an automobile (following automobile) which is present closest to the automobile by a global positioning system (GPS). Also, in the described technique, the host vehicle may be equipped with a following distance measurement device to measure the actual following distance to the preceding vehicle using a laser radar or ultrasonic waves. Then, in the described technique, if the distance between the host vehicle and the preceding vehicle identified by the GPS, and the actual following distance measured by the following distance measurement device substantially match, the vehicle identified by the GPS' and the vehicle recognized by the following distance measurement device are determined to be identical.
Also, for example, Japanese Patent Application Publication No. 2005-5978 (JP-A-2005-5978) describes a technique that measures information on distance and position by an adaptive cruise control (ACC) radar, a GPS, and the like, and obtains information on distance, position, and the like directly from a vehicle that is the other communicating party by an inter-vehicle communication device. Then, in the described technique, by combining these pieces of information with image data around a host vehicle, moving objects that are present in the surroundings are recognized more quickly and more accurately than analysis using only image data. Also, in the described technique, when a plurality of moving objects is present in the vicinity of the host vehicle, this combined process is executed for each of the objects. Furthermore, in the described technique, when the inter-vehicle communication device is unable to detect all the moving objects in the vicinity of the host vehicle within a predetermined period of time due to traffic congestion or human congestion, the range of distance within which the inter-vehicle communication device communicates with moving objects (vehicles, humans, and so on) is set short, thereby narrowing down the number of moving objects to be detected so as to be able to complete communication within a preset time.
Also, for example, Domestic Re-publication of PCT International Application No. WO2005/006275 describes a technique that discriminates a plurality of nearby moving objects by transmitting a travel state including an operational command received by each moving object, together with identification information for the object, and monitoring the behaviors of other moving objects. Also, in the described technique, at least one of the plurality of moving objects is taken as a target, the target is caused to perform a self-indicating action that allows its behavior to be differentiated from other moving objects, and as the other moving objects detect this self-indicating action, the relative position of the target is grasped, thereby discriminating the plurality of moving objects that are present in the surroundings.
However, the control method described in JP-A-2002-222491 is susceptible to error because the traffic density around the vehicle is not taken into consideration when identifying the preceding vehicle.
However, because the surrounding environment recognition system described in JP-A-2005-5978 is configured to obtain information on distance, position, and the like through direct communication with another vehicle equipped with the inter-vehicle communication device, the system is unable to accurately identify the position of a vehicle that is not equipped with the inter-vehicle communication device.
Also, the moving object discrimination method described in WO2005/006275 has a problem that this method cannot be used in situations where the moving object taken as a target is unable to perform such a self-indicating action that allows the moving object to be significantly differentiated from other moving objects. Also, this identification method has a problem in that because it is necessary for other moving objects to respond to and detect the self-indicating action of the target, the method cannot be applied to moving objects that are not equipped with a detection device.